SMB file sharing cannot be modified for migrated users

After upgrading my existing Snow Leopard installation there is no way to modify the filesharing options anymore for migrated users.

Creating a new user and setting the smb filesharing option is no problem.

As soon as I try to disable/enable filesharing for a migrated user account it either ignores the request completely after asking for a password or it asks for a password an responds with incorrect password (which is identical to the login).

So in one way or the other there is some left over from the previous smb implementation which is not understood anymore.

Does anyone know where to look for more specific information regarding the new smb implementation ? Or has a solution for this.

I have been searching and looking around via a terminal but haven't found anything yet.